The disclosure of Japanese Patent Application No. 2000-110633 filed on Apr. 12, 2000, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a combustion heating device, a fuel reforming apparatus including the combustion heating device, and a fuel cell system. More particularly, the invention relates to a combustion heating device adapted to heat a fluid to be heated, by using heat produced by combustion of fuel, a fuel reforming apparatus that includes the combustion heating device and operates to reform hydrocarbon-based fuel into hydrogen-rich fuel gas, and a fuel cell system having the fuel reforming apparatus and a fuel cell that generates electric power when supplied with air and a fuel gas from the fuel reforming apparatus.
2. Description of Related Art
An example of the combustion heating device of the above type is disclosed in, for example, Japanese laid-open Patent Publication No. 8-119602. In this combustion heating device, a mixture of air and methanol supplied as a fuel is heated by means of a heater, and is supplied to a heat exchanger in which a fluid to be heated is heated by using heat generated through catalytic combustion of the fuel. The fluid to be heated may be a reformable material composed of, for example, methanol and water. The combustion heating device is incorporated as a vaporizing section for heating and vaporizing the reformable material as a fluid to be heated, in a methanol reforming apparatus that reforms methanol into a hydrogen-rich fuel gas through steam reforming.
In the above-described combustion heating device, however, methanol as a liquid fuel and air are supplied on the upstream side of a heater. It is therefore often difficult to uniformly mix the liquid fuel and air with each other to provide a homogeneous mixture. If the mixture of fuel and air is not uniformly mixed together, variations arise in the intensity or degree of combustion, in particular, catalyst combustion, resulting in a reduced efficiency with which the fuel is burned, and an accordingly reduced operating efficiency of the combustion heating apparatus.
It is an object of the invention to provide a combustion heating device capable of uniformly mixing air with fuel. It is another object of the invention to provide a combustion heating device that is able to burn fuel in an appropriate manner to yield an improved efficiency. It is still another object of the invention to provide a fuel reforming apparatus capable of efficiently vaporizing at least a portion of a reformable material. It is yet another object of the invention to provide a fuel cell system which provides an improved energy efficiency and/or which is simplified in construction and reduced in size.
To accomplish at least one of the above and other objects, there is provided according to a first aspect of the invention a combustion heating device adapted to beat a fluid to be heated, by using heat generated through combustion of a fuel, comprising: (1) a fuel supply device that supplies the fuel to the device, (2) a vaporizes a remaining portion of the fuel by using heat generated through combustion of the portion of the fuel, (3) a first air supply device that supplies air to be used for combustion of the portion of the fuel by the vaporizing device, and (4) a second air supply device that supplies air to be used for combustion of the remaining portion of the fuel vaporized by the vaporizing device.
In the combustion heating device according to the first aspect of the invention as described above, the first air supply device supplies air to be used for burning a portion of fuel supplied by the fuel supply device, to a vaporizing device in which the remaining fuel is vaporized by using heat generated through combustion of the portion of the fuel, and the second air supply device supplies air to be used for burning the fuel vaporized by the vaporizing device. Namely, the air used for combustion of the fuel during vaporization of the fuel and the air used for combustion of the vaporized fuel are supplied separately or independently of each other. Since the air supplied by the second air supply device is fed into the vaporized fuel, the air and the vaporized fuel can be more uniformly mixed together as compared with a mixture of air and a liquid fuel. Consequently, variations in the intensity or degree of combustion of the fuel can be reduced, and the fuel can be burned with an improved efficiency.
In the combustion heating device as described above, the fuel supply device may spray the fuel into the device. In this case, the vaporizing device can easily vaporize the fuel with improved efficiency.
Also, the combustion heating device of the invention may further include a first air amount control unit that controls an amount of air supplied by the first air supply device, based on an amount of the fuel supplied by the fuel supply device. This makes it possible to supply a more appropriate amount of air for vaporizing the fuel. In this case, the first air amount control unit may control the first air supply device so as to supply an amount of air that is needed for vaporizing the fuel supplied to the device. Thus, the amount of the supplied air can be suitably adjusted not to be greater or less than the amount required for vaporization of the fuel.
Furthermore, the combustion heating device of the invention may further include a second air amount control unit that controls an amount of air supplied by the second air supply device, based on an amount of the fuel supplied by the fuel supply device. This makes it possible to supply a more appropriate amount of air for burning vaporized fuel.
The combustion heating device may further include a heat exchanger that carries a catalyst capable of burning the fuel, and is operable to heat the fluid to be heated, by using heat that is generated when a fuel contained in a mixed gas of the fuel vaporized by the vaporizing device and the air supplied by the second air supply device is burned on the catalyst.
According to a second aspect of the invention, there is provided a fuel reforming apparatus for reforming a hydrocarbon-based fuel into a hydrogen-rich fuel gas, comprising: (a) the combustion heating device according to the first aspect of the invention, and (b) a reforming device that is supplied with the at least one of the hydrocarbon-based fuel and water that has been vaporized by the combustion heating device, and reforms the hydrocarbon-based fuel into the fuel gas through a steam reforming reaction.
In the fuel reforming apparatus as described above, the combustion heating device of the first aspect of the invention is used as a vaporizing section for heating and vaporizing a hydrocarbon-based fuel and/or water as a fluid to be heated, to thus yield substantially the same effects as provided by the combustion heating device. Namely, the fuel can be burned with improved efficiency, so as to highly efficiently heat and vaporize the hydrocarbon-based fuel and/or water as a fluid to be heated.
According to a third aspect of the invention, there is provided a fuel cell system comprising a fuel reforming apparatus adapted to reform a hydrocarbon-based fuel into a hydrogen-rich fuel gas; and a fuel cell that is supplied with the hydrogen-rich fuel gas from the fuel reforming apparatus and the air, so as to generate electric power, wherein the fuel reforming apparatus is constructed according to the second aspect of the invention, and at least one of the first air supply device and the second air supply device supplies air to the fuel cell.
The fuel cell system of the invention, which includes the fuel reforming apparatus according to the second aspect of the invention, yields substantially the same effects as provided by the fuel reforming apparatus as described above. Namely, the fuel can be burned with improved efficiency, so as to highly efficiently heat and vaporize the hydrocarbon-based fuel and/or water as a fluid to be heated. In addition, since the first air supply device and/or the second air supply device is/are used for supplying air to the fuel air, the whole system can be simplified in construction and reduced in size.
The fuel cell system may further include a first cathode exhaust gas supply device that supplies cathode exhaust gas of the fuel cell in addition to or in place of the air supplied by the first air supply device. With this arrangement, exhaust gas emitted from the system can be advantageously reduced.
Also, the fuel cell system may further include a second cathode exhaust gas supply device that supplies a cathode exhaust gas of the fuel cell in addition to or in place of the air supplied by the second air supply device. With this arrangement, too, exhaust gas emitted from the system can be advantageously reduced.
Furthermore, the fuel cell system may further include an anode exhaust gas supply device that supplies an anode exhaust gas of the fuel cell in addition to the air supplied by the second air supply device. With this arrangement, hydrogen contained in the anode exhaust gas of the fuel cell can be effectively utilized for burning the fuel vaporized by the vaporizing device. Consequently, the energy efficiency of the whole system can be improved.